Conventionally, in SiC wafer production, a wafer quality is highly influenced by the quality of the seed crystal during crystal growth (for example, refer to PTL 1). For that reason, a high-quality seed crystal small in the number of crystal defects is important in producing high quality SiC wafers. Therefore, it is essential to strictly manage a high-quality seed crystal during processes and transport, and it is essential to provide a way to prevent a risk (stolen or lost) as high value-added products for the seed crystal that can manufacture the higher quality wafer. In addition, taking means (traceability) for identifying the seed crystal used in the process of manufacturing wafers circulating in the market is effective in prevention of the risk described above. For that reason, up to now, it is general to implement numbering for each wafer in a processing step during the wafer fabrication process, and the above risk is avoided by enabling a manufacturer to be found by numbering confirmation.
However, the numbering is intended to be implemented for identification of the wafer after processing on the wafer, and when crystal growth is performed with the use of the higher quality seed crystal to be subjected to risk avoidance, the history is not automatically imprinted on the wafer. Therefore, when the high-quality seed crystal is obtained by unauthorized means before imprinting, even if the wafer fabrication is conducted by performing crystal growth with the use of the seed crystal, it is impossible to determine whether the seed crystal has been used, or not, and the risk avoidance cannot be attempted. Also, when the SiC wafer cut out from an SiC single crystal grown from the seed crystal is obtained by unauthorized means before imprinting, even if the SiC wafer is newly used as the seed crystal and the wafer is fabricated by the crystal growth, the same as that described above is applied.